Solid state lighting component package with reflective layer

ABSTRACT

A solid state lighting package is provided. The package comprising at least one LED element positioned on a top surface of a substrate or a submount capable of absorbing light emitted by the at least one LED element; and a reflective layer, the reflective layer covering at least a portion of the top surface of the substrate or the submount, whereby at least of portion of the light emitted by the LED element is reflected by the reflective layer. A method of manufacturing a solid state lighting package comprising the reflective layer, and a method of increasing the luminous flux thereof, is also provided.

TECHNICAL FIELD

The present disclosure relates to a solid state lighting package and amanufacturing method thereof, and more specifically, to a solid statelighting package comprising a reflective layer having high reflectivity.

BACKGROUND

Light emitting diodes (LED or LEDs) are solid state devices that convertelectric energy to light, and generally comprise one or more activelayers of semiconductor material sandwiched between oppositely dopedlayers. When a bias is applied across the doped layers, holes andelectrons are injected into the active layer where they recombine togenerate light. Light is emitted from the active layer and from allsurfaces of the LED.

In order to use an LED chip in a circuit or other like arrangement, itis known to enclose an LED chip in a package to provide environmentaland/or mechanical protection, color selection, light focusing and thelike. An LED package also includes electrical leads, contacts or tracesfor electrically connecting the LED package to an external circuit. In atypical LED package 10 illustrated in FIG. 1A, a single LED chip 12 ismounted on a reflective cup 13 by means of a solder bond or conductiveepoxy. One or more wire bond connections 11 connect the ohmic contactsof the LED chip 12 to leads 15A and/or 15B, which may be attached to orintegral with the reflective cup 13. The reflective cup may be filledwith an encapsulant material 16 containing a wavelength conversionmaterial such as a phosphor so that light emitted by the LED at a firstwavelength may be absorbed by the phosphor, which may responsively emitlight at a second wavelength. The entire assembly is then encapsulatedin a clear protective resin 14, which may be molded in the shape of alens to collimate the light emitted from the LED chip 12. While thereflective cup 13 may direct light in an upward direction, opticallosses may occur when the light is reflected (i.e. some light may beabsorbed by the reflector cup due to the less than 100% reflectivity ofpractical reflector surfaces).

A conventional LED package 20 illustrated in FIG. 1B may be more suitedfor high power operations which may generate more heat. In the LEDpackage 20, one or more LED chips 22 are mounted onto a carrier such asa printed circuit board (PCB) carrier, substrate or submount 23. A metalreflector 24 mounted on the submount 23 surrounds the LED chip(s) 22 andreflects light emitted by the LED chips 22 away from the package 20. Thereflector 24 also provides mechanical protection to the LED chips 22.One or more wire bond connections 11 are made between ohmic contacts onthe LED chips 22 and electrical traces 25A, 25B on the submount 23. Themounted LED chips 22 are then covered with an encapsulant 26, which mayprovide environmental and mechanical protection to the chips while alsoacting as a lens. The metal reflector 24 is typically attached to thecarrier by means of a solder or epoxy bond.

Current LED packages (e.g. XLamp™ LEDs provided by Cree, Inc.)incorporate one LED chip and higher light output is achieved at theassembly level by mounting several of these LED packages onto a singlecircuit board. FIG. 2 shows a sectional view of one such distributedintegrated LED array 30 comprising a plurality of LED packages 32mounted to a substrate or submount 34 to achieve higher luminous flux.Typical arrays include many LED packages, with FIG. 2 only showing twofor ease of understanding. Alternatively, higher flux components havebeen provided by utilizing arrays of cavities, with a single LED chipmounted in each of the cavities. (e.g. TitanTurbo™ LED Light Enginesprovided by Lamina, Inc.)

These LED array solutions may be less compact than desired, as theyinclude extended non-light emitting “dead space” between adjacent LEDpackages. This dead space can result in larger devices, and can providefor non-light emitting structures that can absorb light and reduce thetotal luminous flux of the LED package. The above solutions presentchallenges in providing a compact LED lamp structure incorporating anLED component that delivers light flux levels in the 1000 Lumen andhigher range from a small optical source. Moreover, to achieve desiredbeam shapes, individual optical lenses are typically mounted with eachLED component, or very large reflectors (larger than the form ofexisting conventional sources) have to be employed. These secondaryoptical elements (lenses or reflectors) are large and costly, and anylight being reflected from the sidewalls in the packages and cavitiescan also result in additional optical losses, making these overall LEDcomponents less efficient. As a result, the luminance of a LED packageis significantly affected by its package structure.

It is also generally observed that LED's perform best when operatingtemperatures are minimized. Thus, it is generally desirable to removeheat from the LED, typically by heat transfer via the substrate orsubmount. One of the best ceramic substrates for heat transfer isaluminum nitride (AlN). However, at least one problem with AlN as a heattransfer material in a LED package is that it is dark brown in colorupon deposition, which absorbs visible light and reduces the totalluminous flux of the package. Conventional technology is to cover asmuch of the heat transfer material and/or dead space areas withreflective metal, or with white soldermask to maximize reflectivitywhile at the same time providing heat transfer. Unfortunately, metalcannot be applied everywhere in high density LED packages due to itselectrical conductive properties. Typically, a 75-150 micron gap betweenareas of different potential in such packages is provided, which resultsin significant total dead space area having, for example, dark brown AlNin proximity to the light emitting elements. Soldermask is widely usedbecause it is photo-imageable, or screen printable, but the materialproperties and application methods preclude its use in all conditions.White soldermask also discolors after solder reflow or with time andwith photon exposure adding to the other existing problems of lumen lossand color shift. There is also a significant amount of area (e.g., knownas “canyon walls”) between light emitting elements that also absorb orpoorly reflect the luminous light. These conventional solutions are, forthe most part, inadequate for maximizing the total luminous flux of asolid state lighting package.

SUMMARY

The present disclosure provides solutions to the above-mentionedproblems by providing a reflective layer to a solid state lightingpackage and means to apply such reflective layer. The reflective layercomprises a transparent matrix comprising a highly reflective materialdispersed, distributed, and/or suspended therein. The reflective layer,by proper selection of the transparent matrix and the highly reflectivematerial, can also provide electrical insulation to the plurality of LEDelements, such that the spacing between the LED elements and/or otherelements of the LED package can be minimized to the greatest extentpossible. In one aspect, the substrate or submount is or includes one ormore ESD elements, the reflective layer covering at least a portionthereof.

Thus, in a first embodiment, a solid state lighting package is provided.The package comprising at least one LED element positioned on a topsurface of a substrate or a submount capable of absorbing light emittedby the at least one LED element; a reflective layer comprising atransparent matrix comprising a highly reflective material, thetransparent matrix being substantially transparent to wavelengths oflight emitted by the at least one LED element; the reflective layer inproximity to the at least one LED element and covering at least aportion of the top surface of the substrate or the submount, whereby atleast of portion of the light emitted by the LED element is reflected bythe reflective layer.

In a second embodiment, a method of manufacturing a solid state lightingpackage is provided. The method comprising providing at least one LEDelement mounted on a substrate or submount; introducing a transparentmatrix comprising a highly reflective material to the at least one LEDelement and the substrate or submount; and forming a reflective layer inproximity to the at least one LED element and covering at least aportion of the substrate or submount.

In a third embodiment, a method of increasing the luminous flux of asolid state lighting package is provided. The method comprisingproviding a solid state lighting package having at least one LED elementmounted on a substrate or submount capable of absorbing light emitted bythe at least one LED element; providing a reflective layer comprising atransparent matrix comprising a highly reflective material, thereflective layer in proximity to the at least one LED element andcovering at least a portion of the substrate or submount; and reflectinglight emitted by the at least one LED element by the reflective layer,thereby increasing the luminous flux of the solid state lightingpackage.

In a fourth embodiment, a solid state lighting package is provided, thepackage comprising at least one LED element positioned on a top surfaceof a substrate or a submount capable of absorbing light emitted by theat least one LED element; and a reflective layer comprising atransparent matrix comprising a cellular structure capable of reflectingthe light emitted by the LED element, the reflective layer in proximityto the at least one LED element and covering at least a portion of thetop surface of the substrate or the submount, whereby at least ofportion of the light emitted by the LED element is reflected by thereflective layer.

In a fifth embodiment, a method of manufacturing a solid state lightingpackage is provided. The method comprising providing at least one LEDelement mounted on a substrate or submount; introducing a transparentmatrix comprising a foaming agent to the at least one LED element andthe substrate or submount; and forming a reflective layer comprising acellular structure in proximity to the at least one LED element andcovering at least a portion of the substrate or submount.

In a sixth embodiment, a method of increasing the luminous flux of asolid state lighting package is provided. The method comprisingproviding a solid state lighting package having at least one LED elementmounted on a substrate or submount capable of absorbing light emitted bythe at least one LED element; providing a reflective layer covering atleast a portion of the substrate or submount, wherein the reflectivelayer comprises a transparent matrix comprising a cellular structure;and reflecting light emitted by the at least one LED element by thereflective layer, thereby increasing the luminous flux of the solidstate lighting package.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a sectional view of an embodiment of prior art LED lamp;

FIG. 1B shows a sectional view of an embodiment of prior art LED lamp;

FIG. 2 shows a sectional view of one embodiment of a prior art LEDcomponent;

FIG. 3 shows a sectional view of one embodiment of a prior art LEDcomponent;

FIG. 4 is a sectional view of an embodiment of an LED componentaccording to the present disclosure;

FIG. 5 shows a sectional view of one embodiment of a prior art LEDcomponent;

FIG. 6 is a sectional view of an embodiment of another LED componentaccording to the present disclosure;

FIGS. 7A-7F are partial sectional views of FIG. 6 representing alternateembodiments of the present disclosure;

FIG. 8 is a top view of a prior art LED component;

FIG. 9 shows a top view of an LED component according to the presentdisclosure;

FIGS. 10A-10B are sectional views of an embodiment of a single LEDcomponent package according to the present disclosure;

FIGS. 11A-11D are sectional views of a manufacturing embodiment of anLED component according to the present disclosure;

FIG. 12 is a flow chart of a manufacturing embodiment of an LEDcomponent according to the present disclosure;

FIG. 13 is a flow chart of another manufacturing embodiment of an LEDcomponent according to the present disclosure;

FIG. 14 is a flow chart of another manufacturing embodiment of an LEDcomponent according to the present disclosure; and

FIG. 15 is a flow chart of another manufacturing embodiment of an LEDcomponent according to the present disclosure.

DETAILED DESCRIPTION

A solid state lighting package having a reflective layer and amanufacturing method thereof according to exemplary embodiments of thepresent disclosure will be described along with reference to theaccompanying drawings. Reference is made to a solid state lightingpackage, however, any light emitting diode (LED) package is envisagedusing the reflective layer according to the present disclosure. LEDpackages disclosed herein are inclusive of all surface mounted devices(SMD) type packages. Examples of solid state lighting packages includeceramic packages, polyimide packages, lead frame package, andcombinations thereof.

Embodiments of the present invention now will be described more fullyhereinafter with reference to the accompanying drawings, in whichembodiments of the invention are shown. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Like numbers refer to like elements throughout.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present invention. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element such as a layer, region orsubstrate is referred to as being “on” or extending “onto” anotherelement, it can be directly on or extend directly onto the other elementor intervening elements may also be present. In contrast, when anelement is referred to as being “directly on” or extending “directlyonto” another element, there are no intervening elements present. Itwill also be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. It will be understood that these terms areintended to encompass different orientations of the element in additionto any orientation depicted in the figures.

Relative terms such as “below” or “above” or “upper” or “lower” or“horizontal” or “vertical” may be used herein to describe a relationshipof one element, layer or region to another element, layer or region asillustrated in the figures. It will be understood that these terms areintended to encompass different orientations of the device in additionto the orientation depicted in the figures.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”“comprising,” “includes” and/or “including” when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

In a first embodiment, at least one LED element positioned on a topsurface of a substrate or a submount capable of absorbing light emittedby the at least one LED element; and a reflective layer, the reflectivelayer at least partially surrounding the at least one LED element, andcovering at least a portion of the top surface of the substrate or thesubmount, whereby at least of portion of the light emitted by the LEDelement is reflected by the reflective layer is provided. In one aspect,the reflective layer touches the at least one LED element. Thereflective layer comprises a transparent matrix comprising at least onehighly reflective material contained therein. The reflective layer canbe employed in combination with a metal reflector element to increaseluminous efficacy and minimize loss of luminous flux of the LED package.The reflective layer according to the present disclosure can be appliedto a LED package and improve the luminous flux of emitted warm whitelight or cool white light. In another aspect, the reflective layer canbe applied to a LED package and improve a color rendering index ofemitted white light.

In one aspect, the lighting package comprises a plurality of LEDelements in a densely packed arrangement. In one aspect, the pluralityof LED elements are arranged on the substrate so as to form channelstherebetween. In this aspect, the reflective layer is introduced intothe channels between the plurality of LED elements after die attachmentand wire bonding.

Reflective Layer

In one aspect, the reflective layer is comprised of a transparent matrixcomprising a predetermined loading of at least one high index ofrefraction material dispersed, distributed, and/or suspended therein.The transparent matrix can be organic, inorganic, or a mixture thereof.Preferably, the transparent matrix has an index of refraction that islower than that of the high index of refraction material. For example,the transparent matrix can have an index of refraction of less thanabout 1.6, preferably less than about 1.5. Preferably, the transparentmatrix is transparent in the visible spectra and/or at least a portionof the UV region (e.g., from about 200 nanometers to about 850nanometers). Preferably, the transparent matrix is at least 85%transparent in the visible spectra and/or at least a portion of the UVregion corresponding to the wavelength(s) of the LED light emitted fromthe package, more preferably, the transparent matrix is at least 90%transparent, most preferably, the transparent matrix is greater than orequal to at least 95% transparent.

The combination of transparent matrix and highly reflective materialprovides a reflective layer that is generally opaque and/or translucentin appearance, in part due to the loading and/or average particle sizeof the reflective material. In one aspect, the reflective layer afterintroduction to the LED package is a translucent or opaque white oroff-white in appearance. In other aspects, the addition of phosphors tothe reflective layer will provide a colored translucent or opaquereflective layer.

In another aspect, the reflective layer is comprised of a transparentpolymer matrix comprising a cellular foam structure capable ofreflecting the light emitted by the LED element. The foamed transparentpolymer matrix can be organic, inorganic, or a mixture thereof.Preferably, the foamed transparent matrix has a foam cell density and/oraverage cell size sufficient to reflect the incident light of the atleast one LED chip. The cellular foam structure of the transparentmatrix can be open, closed, semi-interconnected, semi-closed, or amixture of any ratio thereof. In some aspects, the average cell diameteris about 0.1 micron to about 50 micron, or about 1 micron to about 10micron. Smaller or larger cell diameters may be used. Particles can beused in the foamed transparent matrix to provide nucleation sites and/orprovide additional reflectivity to the matrix. Suitable particlesinclude highly refractive materials as further discussed below. In otheraspects, the reflective layer comprising a transparent matrix with acellular structure is essentially free of particulate matter. The foamedtransparent matrix can be formed “in-situ” on the LED package usingconventional foaming manufacturing processes for polymers, such as theincorporation of one or more of a gas, a gas-generating compound, and asolvent-extractable compound. Such processes include, but are notlimited to the incorporation of foaming agents such as blowing agents(HFC's, CO₂, N₂, etc), gas-generating compounds (carbonates, azides,etc.) solvent-extractable compounds (NaCl, KCl, etc) and the like intomolten or solvent-cast-able forms of the transparent matrix. The formedfoamed transparent polymer matrix can also be surface textured so as tofurther provide reflectivity of the emitted LED light. In one aspect,spray-in-place foamable polyurethanes and/or poly(meth)acrylicelastomers can be used as the transparent matrix. Leveling and/ormasking techniques may be used to control the application of the foamedtransparent polymer matrix in the LED package.

Suitable transparent matrix materials (and precursor materials) includetransparent organic polymers. Suitable transparent organic polymersinclude silicones, siloxanes, polyesters, polyurethanes, acrylics (e.g.,polyacrylates, polymethacrylates, hereafter “poly(meth)acrylates”),epoxies, fluoropolymers, polyolefins, and co-polymer and/or combinationsthereof. In one aspect polydimethylsiloxanes,polydimethylphenylsiloxanes, polyphenylsiloxanes, or blends areemployed. Other polydialkyl-, polydialkylphenyl-,polydialkylalkylphenyl- and polyalklyphenyl-siloxane polymers can besubstituted for the above transparent matrix. Mixtures, copolymers, andblends of these siloxanes can be used. In one aspect,polydimethylsiloxane and/or polyphenylsiloxanes having sufficientpre-cure viscosities for introduction to the LED package that cure to agel or hard durometer layer are preferred.

The highly refractive material can be any material with a high index ofrefraction. In one aspect, the highly refractive material has an indexof refraction of greater than about 1.8, greater than about 2,preferably greater than about 2.2, and most preferably greater than orequal to about 2.4. Suitable examples of high index of refractionmaterial include inorganic compounds, such as titanium dioxide (n=2.4),zinc oxide, zinc sulfide, barium sulfate, boron nitride, talc, silica,alumina, zeolite, calcium carbonate, magnesium carbonate, bariumsulfate, zinc oxide, titanium oxide, aluminum hydroxide, magnesiumhydroxide, mica, montmorillonite clay, carbon particles, glassparticles, carbon nanotubes, and mixtures thereof. The amount of highindex of refraction material that can be used will at least depend, inpart, on the choice of transparent matrix chosen. To provide suitablereflectivity, while not negatively affecting the viscosity and/or curingand/or dispensability of the transparent matrix, the loading of the highindex of refraction material can be between about 3 weight percent toabout 50 weight percent. Excess amounts of the high index of refractionmaterial may result in delaminating of the reflective layer and/or poordispensing/dispersion of the material in the matrix. Insufficientamounts of the high index of refraction material may result ininsignificant gains in total luminous flux for the package. In oneexemplary aspect, about 6 to about 15 wt. % of the high index ofrefraction material is used in the transparent matrix. In one aspect,the reflective layer is configured so that when introduced to the LEDpackage it will provided the reflective layer at a predeterminedthickness, preferably a thickness less than or equal to the height of alight emitting surface of the substrate/submount mounted LED element.

In certain aspects, the reflective layer is comprised of one or moresolid materials of about 2.4 index of refraction contained in thetransparent matrix of less than about 1.5 index of refraction. Forexample, in one aspect, a predetermined amount of titanium dioxide(TiO₂) comprising a two part, clear silicone matrix can be employed.Titanium dioxide can be present in one or more forms, e.g., rutile,anatase, and brookite. The average particle size of the titanium dioxideparticles in the transparent matrix can be between about 1 nanometer(nanoparticles) to about 500 microns. In certain aspects, the size ofthe titanium dioxide particles is between about 0.1 to about 10 microns,about 0.5 to about 5 microns, or a size distribution mixture can beused. The titanium dioxide can be added to either part (Part A and/orPart B) or both parts of a two-part matrix (e.g., silicone and/or epoxyresin).

In other aspect, the LED package comprises a plurality of LED elementspost die attached and wire bonded, the reflective layer covering atleast a portion of the substrate or submount and at least partiallysurrounding the LED elements. In another aspect, the LED packagecomprises a plurality of LED elements post die attached and wire bonded,the reflective layer covering at least a portion of the substrate orsubmount and touching the LED elements. As discussed further below, thereflective layer is substantially prevented from covering the lightemitting surface(s) of the LED element(s). In one aspect, the reflectivelayer can be configured to be essentially planar with the top surface ofthe LED element(s) so as to improve secondary optics, for example. Thisconfiguration provides LED packages with enhanced brightness byincreasing the amount of reflected light compared to a LED package postdie attached and wire bonded without the reflective layer hereindisclosed. In other aspects the reflective layer is non-planner and/ordoes not completely surround and/or reach the highest vertical height ofthe LED element.

In one aspect as further discussed below, the reflective layer caninclude one or more color shifting elements. The color shifting elementcan be included in the transparent matrix, for example, dispersed ordistributed with the highly reflective material. In other aspects, thecolor shifting element layer can be configured in a separate layer thatcan be adjacent to, on and/or under the reflective layer, e.g., in amulti-layer configuration. In such aspects, different color shiftingelements and/or equal or unequal amounts of one or more color shiftingelements can be distributed among one or more of the multi-layers.Combinations of the above described configurations of transparentmatrix, highly reflective material, and color shifting element can beemployed.

In other aspect, the LED package comprises a plurality of LED elements(arrays) post die attached and wire bonded, the reflective layercovering the substrate or submount and the sidewalls of the LED elementsand channels between the array elements. As discussed further below, thereflective layer is substantially surrounds the edges of the LEDelements, exposes the top surface of the plurality of LED elements, andcovers the substrate surface to which the LED element is attached. Thisconfiguration provides LED packages with enhanced brightness byincreasing the amount of reflected light relative to a LED package postdie attached and wire bonded without the reflective layer hereindisclosed.

LED Packages with Reflective Layer

FIG. 3 shows a conventional LED component 40 comprising a submount 42for holding an array of LED chips, with the submount having die pads 44and conductive traces 46 on its top surface. LED chips 48 are includedthat comprise the LED array, with each of the LED chips 48 mounted to arespective one of the die pads 44. Wire bonds 50 pass between theconductive traces 46 and each of the LED chips 48 with an electricalsignal applied to each of the LED chips 48 through its respective one ofthe die pads 44 and the wire bonds 50. Alternatively, LED chips 48 maycomprise coplanar electrical contacts on one side of the LED (bottomside) with the majority of the light emitting surface being located onthe LED side opposing the electrical contacts (upper side). Suchflip-chip LEDs can be mounted onto the submount 42 by mounting contactscorresponding to one electrode (anode or cathode, respectively) onto thedie pad 44. The contacts of the other LED electrode (cathode or anode,respectively) can be mounted to the traces 46. An optional reflectorelement 52 can be included that is mounted to submount around the LEDchips 48, although in other embodiments the reflector can be arranged indifferent locations and can be shaped differently. One or more of theLED chips 48 in this embodiment can emit at a single color, or one ormore of the LED chips 48 can be coated with a down-converting phosphorwith each type of LEDs being connected at least into one seriesconnection circuit. For example, different color LED's can be arrangedon the substrate, e.g., combinations of blue/green/red LED's, blue LED'swith yellow phosphor adjacent red LED's, and the like. Alternatively,multiple types of LEDs can be simultaneously mounted on the submount 42with independent series circuits, respectively. An optical element inthe form of an encapsulant 54 such as a lens is included over the LEDchips 48.

FIG. 4 shows a LED component 40 a according to the present disclosurehaving beveled-edge LED chips 48 and reflective layer 36 positionedbetween the LED chips 48. In this exemplary aspect, the reflective layer36 essentially surrounds the LED chips 48 and is flush with the lightemitting edge or surface of the LED chips 48 so as to provideessentially a planar surface over the substrate 42 comprised of thereflective layer 36 and the light emitting surface of the LED chips 48.In other aspects, the reflective layer 36 is non-planar and/or containsplanar and non-planar sections, such as an upwards/downwards taper atthe edge of the LED's component and/or in proximity to the metalreflector element 52. In certain aspects, the reflective layer 36essentially surrounds the LED chips. In certain aspects, the reflectivelayer 36 essentially surrounds the light emitting edges of the LEDchips, up to but not including the top surface of the LED chips (notshown). In other aspects, the reflective layer 36 touches the at leastone of the LED chips 48. It is understood that any depiction of a taperof the LED's edge and/or the reflective layer is not limited to thatdepicted in FIG. 4.

The LED component 40 a is shown with three LED chips 48, but it isunderstood that more LED chips can be included. At least some of the LEDchips 48 are interconnected in series to minimize the number of contactsto the LED component and to allow operation with suitable drivers at thedesired drive current, such as in the range of 50 to 150 mA. The “deadspace” between LED chips is typically less than 0.50 mm and as shown inFIG. 4, is at least partially covered by reflective layer 36. In certainaspects, the dead space between LED chips is completely covered by thereflective layer 36. In one embodiment, the spacing is 0.15 mm to 0.01mm depending on the mounting process, allowing for the LED components tobe densely arranged on the top surface of submount 42. This allows forsmaller sized devices that can have a form factor of existing lamps oreven smaller, and can provide the ability to shape the output beam intoa particular angular distribution. Other LED chip spacing dimensions canbe employed, for example, greater than 0.15 mm or less than 0.01 mm. Inother aspects, the LED chip 48 spacing is such that when the reflectivelayer 36 (or its precursor components) is introduced to the array of LEDchips 48, the reflective layer 36 is wicked between the channels formedbetween the individual LED chips 48 of the array. Reflective layer 36preferably is non-conducting, and therefore provides for the ability toreduce the LED array footprint by reducing the spacing betweenindividual LED elements.

FIG. 5 shows a conventional monolithic LED package 60 comprising anarray of LED chips 62 mounted on the surface of a submount 64 withoptical element 66. At least some of the LED chips 62 are interconnectedin a series circuit.

FIG. 6 shows a monolithic LED component 60 a comprising an array of LEDchips 62 mounted on the surface of a submount 64 in accordance with thepresent disclosure. In a manner as discussed below, reflective layer 36is formed between the LED chips 62. The reflective layer 36, which canbe deposited as described below, covers the electrical traces/pads 72,heat transfer materials 39, etc. In this exemplary aspect, thereflective layer 36 essentially surrounds the LED chips 62 and is flushwith the light emitting surface of the LED chips 62 to provideessentially a planar surface comprised of the reflective layer 36 andthe bottom edges of the LED chips 62. In other aspects, the reflectivelayer 36 of a thickness less than the vertical height of the bottomlight emitting surface of the LED elements. In other aspects, thereflective layer 36 is non-planar and/or contains planar and non-planarsections. In certain aspects, the reflective layer 36 completelysurrounds the LED chips 62, providing essentially a planar surface, andis flush with the bottom edge of the light emitting surface of the LEDchips 62.

The LED chips 62 are preferably mounted on a substantially planarsurface of the submount 64 and are arranged under a single optical lenselement. In other embodiments, the LED chips can be mounted on anon-planar substrate or submount. In the embodiment shown, the component60 a can be configured to emit white light at a desired color point andcolor rendering index as a combination of light from the various LEDs,and simultaneously emits a predetermined luminous flux at high efficacy.Use of the reflective layer 36 in this configuration allows for lightthat otherwise would be absorbed to be reflected, providing a net gainin total luminous flux for the LED package. Color shifting elements canbe employed in this configuration.

For example, the LED chips 62 can be coated with one or more phosphorswith the phosphors absorbing at least some of the LED light and emittinga different wavelength of light such that the LED emits a combination oflight from the LED and the phosphor. In one aspect, one or morephosphors can be compounded with the reflective layer 36. For example,the one or more phosphors can be included in the transparent matrixtogether with the highly reflective material. In other aspects, each ofthe LED chips 62 can be coated with one or more color shifting elementsand employed in combination with the reflective layer 36. Thus, in oneaspect, the LED chips 62 can be coated with one or more phosphors andthe reflective layer 36 can be applied on/over the phosphor coatingand/or comprise one or more phosphors.

FIGS. 7A-7E are exploded views of the callout 7A-7E of FIG. 6, depictingalternate embodiments of the combination and/or arrangement of thereflective layer and color shifting elements. Thus, FIG. 7A depicts theLED chip 62 with adjacent phosphor coating 37 at least partiallysurrounded by reflective layer 36. FIG. 7B depicts the reflective layer36 touching the LED chip 62 and at least partially coating substrate 64with the phosphor coating 37 positioned on the reflective layer 36. FIG.7C depicts the phosphor coating 37 at least partially coating substrate64 and touching the LED chip 62 with reflective layer 36 formed on thephosphor coating 37. FIG. 7D depicts the phosphor coating 37 positionedbetween the reflective layers 36. FIG. 7E depicts the reflective layer36 touching the LED chip 62 and at least partially coating heat transfermaterial 39 (e.g. AlN) with the phosphor coating 37 positioned on thereflective layer. FIG. 7F depicts the reflective layer 36 touching theLED chip 62 and the phosphor coating 37 positioned on the LED chip 62.Other possible configurations of the above elements may be employed,such as the phosphor coating 37 at least partially coating the heattransfer material 39 with the reflective layer formed on the phosphorcoating 37.

In one exemplary embodiment according to the present disclosure, the LEDchips 62 are configured to provide a resultant white light, e.g., coolwhite or warm white. For example, LEDs chips 62 can have an LED thatemits light in the blue wavelength spectrum and the phosphor absorbssome of the blue light and re-emits yellow, with the LED chips 62emitting a white light combination of blue and yellow light. In oneembodiment, the phosphor comprises commercially available YAG:Ce,although a full range of broad yellow spectral emission is possibleusing conversion particles made of phosphors based on the(Gd,Y)₃(Al,Ga)₅O₁₂:Ce system, such as the Y₃Al₅O₁₂:Ce (YAG). Otheryellow phosphors that can be used for white emitting LED chips include,for example: Tb_(3-x)RE_(x)O₁₂:Ce(TAG); RE=Y, Gd, La, Lu; orSr_(2-x-y)Ba_(x)Ca_(y)SiO₄:Eu.

The LED chips 62 can be configured for emitting red light, for example,they can comprise LED structures and materials that permit emission ofred light directly from the active region. Alternatively, in otherembodiments, the LED chips 62 can comprise LEDs covered by a phosphorthat absorbs the LED light and emits a red light. Some phosphorsappropriate for these structures can comprise, for example: RedLu₂O₃:Eu³⁺ (Sr_(2-x)La_(x))(Ce_(1-x)Eu_(x))O₄ Sr₂Ce_(1-x)Eu_(x)O₄Sr_(2-x)Eu_(x)CeO₄ SrTiO₃:Pr³⁺, Ga³⁺ CaAlSiN₃:Eu²⁺ Sr₂Si₅N₈:Eu². Otherstructures, arrangements, and combinations of single and/or multi-colorLED-phosphor chips can be employed to provide a desired lighting effect,as is generally known in the art.

The submount 64 can be formed of many different materials with apreferred material being electrically insulating, such as a dielectricelement, with the submount being between the LED array and the componentbackside. The submount can comprise a ceramic such as alumina, aluminumnitride, silicon carbide, or a polymeric material such as polyimide andpolyester etc. In the preferred embodiment, the dielectric material hasa high thermal conductivity such as with aluminum nitride and siliconcarbide.

In other aspects of the above embodiments, the submount 64 can alsocomprise additional highly reflective material, such as reflectiveceramic or metal layers like silver, to enhance light extraction fromthe component and/or complement the reflective layer 36. The surface ofthe submount 64 can be pre-treated with adhesion promoters and/orcoupling agents known in the art to improve the adhesion of thereflective layer 36 to the surface of the submount, sides/edges of theLED chips providing that such adhesion methods do not substantiallydegrade the performance of the LED elements or package.

In other embodiments the submount 64 can comprise a printed circuitboard (PCB), alumina, sapphire or silicon or any other suitablematerial, such as T-Clad thermal clad insulated substrate material,available from The Bergquist Company of Chanhassen, Minn. For PCBembodiments, different PCB types can be used such as standard FR-4 PCB,metal core PCB, or any other type of printed circuit board.

It is understood that LED components according to the present disclosurecan be fabricated using a method that incorporates submount panel orwafer comprising a plurality of submounts. Each of the submounts 64 canbe formed with its own array of LEDs and optical elements 66 such thatmultiple LED chips 62 can be formed across the submount panel. MultipleLED chips 62 can then be singulated from the submount panel. Eachsubmount 64 may also comprise a more complex combination of elementssuch as a plurality of “submount” assemblies which are mounted on aplanar surface of submount. As more fully described below, the submountassemblies can have different functionalities such as providingelectrostatic discharge (ESD) protection for the various LED chips. Insuch embodiments, the reflective layer 36 can be employed as describedabove so that the reflective layer 36 essentially surrounds the LEDchips and is flush with the top surface of the LED chips.

The size of the submount 64 in LED package 60 can vary depending oncertain factors such as the size and number of LEDs. In one embodiment,the sides of the submount can be approximately 12 mm by 13 mm. It isfurther understood that the submount 64 can have other shapes includingcircular, oval, rectangular, hexagonal or other multiple sided shapes.

Referring now to FIG. 8, the top surface of a conventional submount 64is shown having planar surface with patterned conductive features 68that can include die attach pads 70 and interconnecting conductivetraces 72. These features 68 provide conductive paths for electricalconnection to the LED chips 62 using known contacting methods. Each ofthe LED chips 62 (not shown) can be mounted to a respective one of theattach pads 70 using known methods and material mounting usingconventional solder materials that may or may not contain a fluxmaterial. The LED chips 62 can similarly be mounted and electricallyconnected to the conductive traces 72 using known surface mount or wirebonding methods depending on the geometry of the LED chips 62.Alternatively, flip chip LEDs can be mounted as described above on theattach pads and conductive traces. The attach pads 70 andinterconnecting traces 72 can comprise many different materials, such asmetals or other conductive materials, and in one embodiment they cancomprise copper deposited using known techniques such as plating.

Referring now to FIG. 9, the top surface of the submount 64 according tothe present disclosure is shown having planar surface with reflectivelayer 36 covering its patterned conductive features 68 a (not shown, butsimilar to that of FIG. 8) that can include die attach pads andinterconnecting conductive traces 72. Each of the LED chips 62 (notshown) preferably can be pre-mounted and wire bonded to a respective oneof the attach pads using known methods and material mounting usingconventional solder materials that may or may not contain a fluxmaterial. As discussed below, the LED chips preferably can similarly bepre-mounted and electrically connected to conductive traces using knownsurface mount or wire bonding methods depending on the geometry of theLED chips 62 prior to introduction and/or forming of the reflectivelayer 36. The reflective layer 36 can be configured to provideessentially a planar surface that includes the top face of the LED chipsand the reflective layer 36 as described above. In one aspect, the arraycomprises flip chip LEDs mounted as described above on the attach padsand conductive traces.

In another embodiment, single LED element luminary packages can also beprovided. Thus, FIGS. 10A and 10B depict LED packages including thereflective layer 36 as described above. FIG. 10A depicts a high powerLED package 30 a, with one LED chip 22, mounted onto a carrier such as aprinted circuit board (PCB) carrier, substrate or submount 23.Reflective layer 36 is shown at a thickness essentially equal to thelight emitting surface of LED chip 22. In other aspects, the reflectivelayer 36 is of a thickness (height) such that it is flush with the topsurface of the LED chip 22. A metal reflector 24 mounted on the submount23 surrounds the LED chip 22. One or more wire bond connections 11 aremade between ohmic contacts on the LED chips 22 and electrical traces25A, 25B on the submount 23. The mounted LED chip 22 and reflectivelayer 36 are then covered with an encapsulant 26, which may provideenvironmental and mechanical protection to the chips while also actingas a lens. The metal reflector 24 is typically attached to the carrierby means of a solder or epoxy bond. Other configurations of the singleLED luminary of FIG. 10A, with reflective layer 36 can be employed, forexample, such as a flip-chip configuration.

FIG. 10B depicts a flip chip LED package 30 b having a single,beveled-edge LED chip 48 emitting light 61, and reflective layer 36positioned between the LED chip 48 and the metal reflector element 52.In this exemplary aspect, the reflective layer 36 essentially surroundsthe LED chip 48 and is flush with the lower light emitting edge orsurface of the LED chip 48, covering substrate 34. In other aspects, thereflective layer 36 is of a thickness (height) such that it is flushwith the top surface of the LED chip 48.

Thus, the present disclosure is directed to application of thereflective layer on many different LED chip arrangements. In otheraspects, application of the reflective layer on many different LED chiparrangements with the individual LED chips either coated by a convertingphosphor or emitting light directly from their active region, areprovided. In one alternative embodiment, a single or plurality of seriesconnected LED chip circuits can comprise LED chips wherein all arecoated with a single down-converting material. The mixed emission fromthe LED and the down-converting material can be cool or warm light. Inone embodiment, all the LED chips emitter are blue LEDs covered withphosphor. In certain aspects, the phosphor can be incorporated into thereflective layer and used in combination coated LED chips.

It is understood that the LED chips in the arrays including thereflective layer as herein disclosed and described can be arranged asone or more multiple multi-chip LED lamps as described in U.S. PatentPublication No. 2007/0223219 entitled “Multi-Chip Light Emitting Devicefor Providing High-CRI Warm White Light and Light Fixtures Including theSame”, the disclosure of which is incorporated by reference.

Another embodiment can comprise a single or plurality of seriesconnection LED circuits, with all the LED chips comprising LEDs beingcoated with and/or containing the reflective layer 36 comprising two ormore down-converting materials like a phosphor. The combined LED andphosphor emission can cover different spectral ranges such as blue,green, yellow and red spectral ranges. The mixed emission can be cool orwarm white light with a color point on the black body locus or within an8-step Mac Adam ellipse thereof with high color rendering index ofgreater that 85. The phosphor composition can be for example selectedfrom materials discussed above and/or combined with the reflectivelayer.

In still other embodiments of an LED component according to the presentdisclosure can comprise a plurality of series connection circuitscomprising LED chips that emit light directly from their active region,with at least one series circuit provided for red, green and blueemitting LEDs, respectively. In other embodiments series connected LEDscircuits can also be added emitting cyan, yellow and/or amber. The LEDcomponent preferably emits a white light combination of light from theseries circuits that has a high color rendering index of greater than85. The reflective layer can comprise a plurality of highly reflectivematerials each of which is chosen to maximize reflection of acorresponding wavelength of light from such an array of LED chips.Likewise, the transparent matrix of the reflective layer can be chosento maximize the transmission of the many wavelengths of light and/or toattenuate a predetermined wavelength(s) of light for a particularoptical affect.

Still other embodiments can comprise different LED chips with LEDsemitting at different wavelengths. For example, in any of the LED chipconfigurations above in which at least one of the emitters comprises ashort wavelength emitter in conjunction with one or more phosphoremitters, an ultraviolet emitting LED can be used as the LED. Thetransparent matrix of the reflective layer preferably is substantiallytransparent in the UV region associated with the ultraviolet emittingLED (e.g., polydimethylsiloxanes). This results in the predominantemission component of the LED chips coming from the phosphor excited bythe ultraviolet LED. The phosphor emitter can be included in thetransparent matrix or applied to the package separately in combinationwith the reflective layer. By way of example, each of the followingphosphors exhibits excitation in the UV emission spectrum, provides adesirable peak emission, has efficient light conversion, and hasacceptable Stokes shift, for example: Yellow/Green:(Sr,Ca,Ba)(Al,Ga)₂S₄:Eu²⁺ Ba₂(Mg,Zn)Si₂O₇:Eu²⁺Gd_(0.46)Sr_(0.31)Al_(1.23)O_(x)F_(1.38):Eu²⁺ _(0.06)(Ba_(1-x-y)Sr_(x)Ca_(y))SiO₄:Eu Ba₂SiO₄:Eu²⁺.

The LED components according to the present disclosure are particularlyapplicable to integration is solid state lighting luminares, and providefor surface mount or wire bond mounting in the luminares. The LEDcomponents provide an improvement in the lumens provided per cost, dueto the reduced assembly requirements and footprint in luminaries alongwith reduced driver costs. The use of the reflective layer in accordancewith the present disclosure provides for improved luminous flux and canbe achieved with low cost materials and minimum additional manufacturingcosts.

Forming the Reflective Layer

In another embodiment of the present disclosure, a method of forming thereflective layer for a LED package capable of improving luminousefficacy and minimizing loss of luminous flux is provided. Thus, amanufacturing method is provided comprising providing a solid statelighting package comprising: at least one LED element mounted on a topsurface of a substrate or submount and introducing a reflective layer tothe at least one LED element and covering a least a portion of the topsurface of the substrate or submount. In one aspect, the methodcomprises providing a solid state lighting package comprising: aplurality of LED elements mounted on a top surface of a substrate orsubmount, the plurality of LED elements arranged so as to form channelstherebetween; and introducing a low index of refraction transparentmatrix comprising a high index of refraction material dispersed,distributed, or suspended therein to the channels; and forming areflective layer around the at least one LED element and a least aportion of the top surface of the substrate or submount.

Thus, in one exemplary embodiment, there is provided a solid statelighting package comprising: a substrate or submount having attachedthereto at least one LED element; and a reflective layer formed aroundthe at least one LED element and covering at least a portion of thesubstrate or submount surface. The reflective layer can be of a verticalheight relative to the LED chips that is a height flush with the topsurface of the LED chips (e.g., surrounding and/or touching the verticalsides of the LED chips) or can be of any height less than the topsurface of the LED chips.

In one aspect, the reflective layer can be produced by providing atransparent matrix material and dispersing, distributing, and/orsuspending one or more of a foaming agent and/or a highly reflectivematerial using known compounding and/or dispersive/distributive mixingtechniques. In certain aspects, the transparent matrix is a two-part,curable formulation. In such aspects, the one or more of foaming agentand/or highly reflective material can be introduced to either or both ofthe two-part portions, provided that it does not substantially affectthe curing of the matrix. Thus, for example, a predetermined amount oftitanium dioxide can be added to one part of a two-part curable siliconeresin to provide a precursor formulation suitable for use as describedbelow. In another aspect, the transparent matrix can be introduced tothe substrate or submount and then the one or more foaming agent and/orhighly reflective material can be incorporated in the transparentmatrix. Incorporation includes providing an equal distribution orconcentration gradient of the one or more foaming agent and/or highlyreflective material in the thickness of the transparent matrix.

With reference to FIGS. 11A-11D, one aspect of the presently disclosedmethod is described, where the reflective layer is introduced to apreviously post die attached and wire bonded LED element(s) withsubsequent formation of a metal reflective element. Thus, FIG. 11Adepicts an array of mounted LED chips 48 on substrate 42 having die pads44 and conductive traces 46 and wire bonds 50. FIG. 11B depicts afterintroduction of the reflective layer 36 at least partially covering thesubstrate 42 and surrounding die pads 44, 46. The reflective layer 36can be a vertical height relative to the LED chips that is a heightflush with the top surface of the LED chips (e.g., surrounding and/ortouching the vertical sides of the LED chips) or can be of any heightless than the top surface of the LED chips. FIG. 11C depicts afterbonding of the metal reflective element 52. Masking techniques can beused to introduce and/or remove portions of the reflective layer 36 fromsubstrate 42 to provide for bonding of the metal reflective element 52to the substrate 42. FIG. 11D depicts after introduction of theencapsulant 54 to provide LED package 40 c.

With reference to FIG. 12, describing the manufacturing method of thesolid state lighting package, flow chart 300, step 301 includesproviding at least one LED element mounted on a substrate or submount,the substrate or submount capable of absorbing the light emitted by theLED element. Step 303 refers to the introduction of the transparentmatrix comprising the highly reflective material to the at least one LEDelement and substrate. Step 305 refers to the forming of the reflectivelayer in proximity to the LED element, and covering a least a portion ofthe substrate or submount. Masking techniques can be used to introduceand/or remove portions of the reflective layer. The reflective layer canbe of a vertical height relative to the LED chips that is a height flushwith the top surface of the LED chips (e.g., surrounding and/or touchingthe vertical sides of the LED chips) or can be of any height less thanthe top surface of the LED chips. Step 307 refers to the optionalmounting of a metal reflective element to the substrate.

With reference to FIG. 13 and flow chart 400, an aspect of themanufacturing method is provided, where step 401 includes providing anarray of LED elements mounted on a substrate or submount, the substrateor submount capable of absorbing the light emitted by the LED element.The array of LED elements provide for one or more channels between theLED chips. The size of the array can be small (e.g., 2×2) or large(>2×>2). Step 403 refers to the introduction of the transparent matrix(the foamed transparent polymer matrix and/or the transparent matrixcomprising the highly reflective material as described above) of aviscosity to wick the reflective layer (or its pre-cured precursor(s))into the one or more channels formed by the LED chips of the array andsubstrate. The combined viscosity of the matrix (e.g., pre-cured,two-part formulation, curable one-part formulation, ormolten/solvent-castable formulation) is preferably chosen so as toprovide for wicking or capillary drawing of the formulation in-betweenthe spacing or channels of arrayed LED elements. This provides for theintroduction of the reflective layer on planar or non-planar substrates.Once the pre-cured, combined two-part transparent matrix material hasbeen wicked between the LED elements and has leveled to a predeterminedheight relative to that of the light emitting surface of the LEDelements, the matrix is allowed to (optionally foam), cure, harden, orset. Curing can be performed with or without the use of heat and/orlight. While the above example is exemplified by using to a two-partsilicone matrix, other suitable transparent matrixes can be substitutedand configured with the predetermined loading of one or more of foamingagent and/or highly reflective material and viscosity adjusted toprovide for the introduction thereof about the LED elements as describedabove. For example, a transparent matrix comprising one or more of thefoaming agent and/or the highly reflective material can be melted at atemperature below the solder flow point and introduced to the LED chipsand substrate, the melted matrix having a viscosity capable of providingwicking. Alternatively, the transparent matrix and one or more of thefoaming agent and/or the highly reflective material can besolvent-diluted to a sufficient viscosity to provide wicking and thenthe solvent driven off (and optionally foamed) using heat. Step 405refers to forming of the reflective layer to the LED element andcovering a least a portion of the substrate or submount. The reflectivelayer can be of a vertical height relative to the LED chips that is aheight flush with the top surface of the LED chips (e.g., surroundingand/or touching the vertical sides of the LED chips) or can be of anyheight less than the top surface of the LED chips. Step 407 refers tothe optional mounting of a metal reflective element to the substrate.

With reference to FIG. 14, describing the manufacturing method of thesolid state lighting package, flow chart 500, step 501 includesproviding at least one LED element mounted on a substrate or submount,the substrate or submount capable of absorbing the light emitted by theLED element. Step 503 refers to the introduction of the transparentmatrix comprising the foaming agent to the at least one LED element andsubstrate. Step 505 refers to the forming of the reflective layercomprising a cellular structure in proximity to the LED element andcovering a least a portion of the substrate or submount. The cellularstructure is configured to reflect light emitted by the at least one LEDelement. Masking techniques can be used to introduce and/or removeportions of the reflective layer. The reflective layer can be of avertical height relative to the LED chips that is a height flush withthe top surface of the LED chips (e.g., surrounding and/or touching thevertical sides of the LED chips) or can be of any height less than thetop surface of the LED chips. Step 507 refers to the optional mountingof a metal reflective element to the substrate.

With reference to FIG. 15 and flow chart 600, another aspect of themanufacturing method is provided, where the transparent matrix isintroduced to the at least one LED element mounted on a substrate orsubmount and subsequently the highly reflective material and/or foamingagent is introduced to the transparent layer. Thus, step 601 includesproviding at least one LED element mounted on a substrate or submount.Step 603 refers to the introduction of the transparent matrix. Maskingtechniques can be used to introduce and/or remove portions of thetransparent matrix. In one aspect, the transparent matrix has aviscosity sufficient to wick the transparent matrix (or its pre-curedprecursor(s)) into the one or more channels formed by an array of LEDchips mounted to the substrate. The combined viscosity of the matrix ispreferably chosen so as to provide for wicking or capillary drawing ofthe formulation in-between the spacing or channels of arrayed LEDelements. This provides for the introduction of the transparent matrixon planar or non-planar substrates. Step 605 refers to introducing oneor more of a foaming agent and/or a highly reflective material to thetransparent matrix, for example, after introduction of the transparentmatrix. In one aspect, the foaming agents and/or the highly reflectivematerial are introduced to the transparent matrix before set-up (e.g.,while “tacky”). In one aspect, the at least one foaming agent and/orhighly reflective material deposited on the transparent matrix can becontacted (e.g., coated, sprayed, etc.) with the same or different(e.g., harder durometer, different optical properties, etc.) transparentmatrix to form a layered structure securing the foaming agent and/orhighly reflective material. Alternatively or in combination, solvents(e.g., liquids and/or supercritical fluids) and/or heat can be used tourge the foaming agents and/or highly reflective material into thetransparent matrix. Step 607 refers to forming of the reflective layer.Once the pre-cured, combined two-part transparent matrix material hasbeen introduced (or wicked) between the LED elements and has leveled toa predetermined height relative to that of the light emitting surface ofthe LED elements, the matrix is allowed to foam, cure, harden, or set asdescribed above. Excess foaming agent and/or highly reflective materialcan be subsequently removed upon curing. Curing/foaming can be performedwith or without the use of heat and/or light. The transparent matrix canbe foamed to comprise cells of an average diameter and of a densitysufficient to reflect the emitted LED light. The reflective layer isformed so as to surround and/or touch the LED element and cover a leasta portion of the substrate or submount. The reflective layer can be of avertical height relative to the LED chips that is a height flush withthe top surface of the LED chips (e.g., surrounding and/or touching thevertical sides of the LED chips) or can be of any height less than thetop surface of the LED chips. Step 609 refers to the optional mountingof a metal reflective element to the substrate.

Increasing Luminous Flux

Table 1 summarizes the gain in total luminous flux for an array (2×3) ofLED chips manufactured with the reflective layer according to thepresent disclosure compared to a similar array without the reflectivelayer.

TABLE 1 Mean Lm/W³ for controls and LED arrays with reflective layer.TiO2Mix = titanium dioxide 11.7 weight percent in polydimethylsiloxaneresin. Mean Net % Gain Die Substrate Treatment String (LF380mA) in LFWZ1400 2 × 3 Control All-on 465.89 — WZ1400 2 × 3 Control All-on 236.28— WZ1400 2 × 3 Control B-on 247.28 — WZ1400 2 × 3 TiO2Mix All-on487.53 >4.6 WZ1400 2 × 3 TiO2Mix A-on 246.91 >4.2 WZ1400 2 × 3 TiO2MixB-on 258.35 >4.2

Table 2 summarizes the gain in total luminous flux for (2×3) and (2×7)arrays of LED chips manufactured with the reflective layer according tothe present disclosure compared to a similar array without thereflective layer. As shown in Tables 1-2, the reflective layer providedsignificant total mean luminous flux gains compared to control for LEDchips powered up to 350 mA or more. Similar results were obtained forlarger arrays (2×7) and for 150 mA drive currents. Thus, the luminousintensity and the total luminous flux increases as a function of the LEDdensity of the package size. It was observed that for a power input ofbetween about 150 mA to about 380 mA, and a LED array of between about 6to about 14 LED elements, the gain in mean luminous flux (lumen/W) isincreased more than about 3.5% when compared to a solid state lightingpackage at a similar power input and having a similar array arrangementand number of LED elements without the reflective layer. Gains of morethan 4% were observed for large arrays, e.g., 2×7. For a single LED, thenet gain in luminous flux was small, but measurable.

TABLE 2 Mean Lm/W for controls and LED arrays with reflective layer.TiO2Mix = titanium dioxide 11.7 weight percent in polydimethylsiloxaneresin. Mean Net % Die Substrate Treatment String (LF150 mA) Gain in LFWZ1400 2 × 3 Control 205.9 — WZ1400 2 × 3 TiO2Mix 215.6 >4.2 WZ850 2 × 7Control 628.9 — WZ850 2 × 7 TiO2Mix 653.2 >3.8

As shown in Tables 1 and 2, the solid state lighting package includingthe reflective layer of the present disclosure significantly increasesthe luminous efficacy as compared to a similar solid state lightingpackage without the reflective layer. Similar results were observed orcan be expected for various packages including packages having metalreflectors and the like.

As the reflective layer is readily adaptable to a post-mounted, wirebonded LED package, with the reflective layer being readily introducedto the LED edges and channels in-between, minimal modification toexisting LED packaging manufacturing is needed. The methods according tothe present disclosure are adaptable to monolithic LED structures withor without metal reflector elements and/or modification of thereflector.

The reflective layer and methods of manufacturing, and methods ofincreasing the total luminous flux of a solid state lighting package aregenerally applicable to a variety of existing lighting packages, forexample, XLamp products XM-L, ML-B, ML-E, MP-L EasyWhite, MX-3, MX-6,XP-G, XP-E, XP-C, MC-E, XR-E, XR-C, and XR LED packages manufactured byCree, Inc. The benefits in luminous flux can be applied to many lightingapplications, for example, commercial/retail display spotlights, LEDretrofit bulbs, and other indoor and outdoor general-illuminationapplications.

The above has been described both generically and with regard tospecific embodiments. Although the present disclosure has been set forthin what is believed to be the preferred embodiments, a wide variety ofalternatives known to those of skill in the art can be selected withinthe generic disclosure. Other advantages and obvious modifications ofthe present disclosure will be apparent to the artisan from the abovedescription and further through practice of the present disclosure.

1. A solid state lighting package comprising: at least one LED elementpositioned on a top surface of a substrate, the at least one LED elementhaving a vertical edge height from the substrate, the substrate or thesubmount capable of absorbing light emitted by the at least one LEDelement; and a reflective layer comprising a transparent matrixcomprising a highly reflective material, the transparent matrix beingsubstantially transparent to wavelengths of light emitted by the atleast one LED element; the reflective layer in proximity to the at leastone LED element and covering at least a portion of the top surface ofthe substrate, the reflective layer height from the substrate being lessthan the vertical edge height of the at least one LED element, wherebyat least of portion of the light emitted by the LED element is reflectedby the reflective layer.
 2. The solid state lighting package of claim 1,wherein the reflective layer touches the at least one LED element. 3.The solid state lighting package of claim 1, wherein the reflectivelayer essentially surrounds the at least one LED element.
 4. The solidstate lighting package of claim 1, wherein the reflective layercomprises a transparent matrix having an index of refraction of betweenabout 1.4 and about 1.5, and a highly reflective material having anindex of refraction of between about 1.8 to about 2.4.
 5. The solidstate lighting package of claim 1, wherein the transparent matrix is atleast one of a polysiloxane, polyurethane, polyimide,poly(meth)acrylate, epoxy, fluoropolymer, and combinations thereof. 6.The solid state lighting package of claim 1, wherein the transparentmatrix is at least one of a polydialkylsiloxane,polydialkylphenylsiloxane, polydialkylalkylphenylsiloxane, andpolyalklyphenylsiloxanes, or blends thereof.
 7. The solid state lightingpackage of claim 1, wherein the highly reflective material is at leastone of titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, boronnitride, talc, silica, alumina, zeolite, calcium carbonate, magnesiumcarbonate, barium sulfate, zinc oxide, aluminum hydroxide, magnesiumhydroxide, mica, montmorillonite clay, carbon particles, glassparticles, carbon nanotubes, and mixtures thereof.
 8. The solid statelighting package of claim 5, wherein the at least one ofpolydimethylsiloxane and polyphenylsiloxane comprises a two partmixture, the highly reflective material being present in one or both ofthe two part mixture.
 9. The solid state lighting package of claim 1,wherein the reflective layer comprises titanium dioxide and at least oneof polydimethylsiloxane and polyphenylsiloxane.
 10. The solid statelighting package of claim 9, wherein the titanium dioxide is present inan amount of between about 3 to about 25 weight percent.
 11. The solidstate lighting package of claim 1, further comprising a color shiftingelement.
 12. The solid state lighting package of claim 1, wherein the atleast one LED element comprises an array of LED elements.
 13. The solidstate lighting package of claim 1, wherein the substrate comprisesaluminum nitride.
 14. A method of manufacturing a solid state lightingpackage comprising: drawing, by capillary action, a transparent matrixcomprising a highly reflective material to between at least one channelformed from an array of LED elements mounted on a substrate thesubstrate; forming a reflective layer in proximity to the at least oneLED element and covering at least a portion of the substrate; andavoiding covering any part of the LED element.
 15. The method of claim14, wherein the at least one LED element is post die attached and wirebonded to the substrate before forming the reflective layer. 16.(canceled)
 17. The method of claim 14, wherein the reflective layeressentially surrounds the at least one LED element.
 18. The method ofclaim 14, wherein the reflective layer thickness is equal to or lessthan a vertical height of a light emitting surface the at least one LEDelement from the substrate.
 19. The method of claim 18, wherein thereflective layer thickness is less than the vertical height of the lightemitting surface of at least one LED element from the substrate. 20.(canceled)
 21. (canceled)
 22. The method of claim 14, wherein thetransparent matrix is a two part curable material and together with thehighly reflective material having an uncured viscosity capable of beingdrawn by capillary action into the at least one channel.
 23. The methodof claim 14, wherein the transparent matrix has an index of refractionof between about 1.4 and about 1.5 and the highly reflective materialhas an index of refraction of between about 1.8 and about 2.4.
 24. Themethod of claim 14, wherein the highly reflective material is at leastone of titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, boronnitride, talc, silica, alumina, zeolite, calcium carbonate, magnesiumcarbonate, barium sulfate, zinc oxide, aluminum hydroxide, magnesiumhydroxide, mica, montmorillonite clay, carbon particles, glassparticles, carbon nanotubes, and mixtures thereof.
 25. The method ofclaim 14, wherein the transparent matrix is at least one of apolysiloxane, polyurethane, polyimide, poly(meth)acrylate, epoxy,fluoropolymer, and combinations thereof.
 26. The method of claim 14,wherein the transparent matrix is at least one of a polydialkylsiloxane,polydialkylphenylsiloxane, polydialkylalkylphenylsiloxane, andpolyalklyphenylsiloxanes, or blends thereof.
 27. The method of claim 15,wherein the reflective layer comprises titanium dioxide and at least oneof polydimethylsiloxane and polyphenylsiloxane.
 28. The method of claim14, wherein the transparent matrix is comprises a two part curablemixture and the forming step comprising curing the transparent matrix.29. (canceled)
 30. The method of claim 14, further comprising coveringthe highly reflective material with a different transparent matrix. 31.A method of increasing the luminous flux of a solid state lightingpackage, the method comprising: providing a solid state lighting packagehaving at least one LED element mounted on a substrate capable ofabsorbing light emitted by the at least one LED element; providing areflective layer comprising a transparent matrix comprising a highlyreflective material, the reflective layer in proximity to the at leastone LED element and covering at least a portion of the substrate orsubmount; and reflecting light emitted by at least one LED elementmounted on a substrate by a reflective layer comprising a transparentmatrix comprising a highly reflective material, the reflective layer inproximity to the at least one LED element and covering at least aportion of the substrate, the reflective layer height from the substratebeing less than or flush with a bottom edge height of the at least oneLED element, thereby increasing the luminous flux of the solid statelighting package.
 32. The method of claim 31, wherein the at least oneLED element is post die attached and wire bonded to the substrate beforeforming the reflective layer.
 33. (canceled)
 34. The method of claim 31,wherein the reflective layer essentially surrounds the at least one LEDelement.
 35. (canceled)
 36. The method of claim 32, wherein thereflective layer thickness is less than the vertical height of thebottom edge height of the at least one LED element from the substrate.37. The method of claim 31, wherein the transparent matrix has an indexof refraction of between about 1.4 and about 1.5 and the highlyreflective material has an index of refraction of between about 1.8 andabout 2.4.
 38. The method of claim 31, wherein the highly reflectivematerial is at least one of titanium dioxide, zinc oxide, zinc sulfide,barium sulfate, boron nitride, talc, silica, alumina, zeolite, calciumcarbonate, magnesium carbonate, barium sulfate, zinc oxide, aluminumhydroxide, magnesium hydroxide, mica, montmorillonite clay, carbonparticles, glass particles, carbon nanotubes, and mixtures thereof. 39.The method of claim 31, wherein the transparent matrix is at least oneof a polysiloxane, polyurethane, polyimide, poly(meth)acrylate, epoxy,fluoropolymer, and combinations thereof.
 40. The method of claim 31,wherein the transparent matrix is at least one of a polydialkylsiloxane,polydialkylphenylsiloxane, polydialkylalkylphenylsiloxane, andpolyalklyphenylsiloxanes, or blends thereof.
 41. The method of claim 31,wherein the reflective layer comprises titanium dioxide and at least oneof polydimethylsiloxane and polyphenylsiloxane.
 42. The method of claim31, wherein the substrate comprises aluminum nitride.
 43. The method ofclaim 31, wherein the at least one LED element comprises an array of LEDelements.
 44. The method of claim 43, wherein the reflective layerprovides for a substantially planar surface across the substrate betweenthe array of LED elements.
 45. The method of claim 31, wherein the solidstate lighting package comprises an array of between about 6 to about 14LED elements wherein at a power input of between about 150 mA to about380 mA, the gain in mean luminous flux (lumen/W) is increased more thanabout 3.5% when compared to a solid state lighting package at a similarpower input and having a similar array arrangement and number of LEDelements without the reflective layer. 46-85. (canceled)